The release of insulin by a normal human pancreas in response to elevated glucose levels is known to consist of two phases. The first phase consists of a rapid increase in plasma insulin levels, reaching a maximum within a few minutes of the hyperglycemic stimulus. Plasma insulin levels decrease sharply after the first phase of insulin secretion, and a second, more gradual peak in plasma insulin levels (the second phase) is observed several hours later. A reduction in the first phase of insulin secretion by the pancreas is the earliest detectable abnormality in patients destined to develop type 2 diabetes. J. E. Gerich, Diabetes, Vol. 51, Supplement 1, February 2002, S117-S121, the entirety of which is hereby incorporated by reference. Accordingly, a need exists for a drug delivery device that supplies the missing first phase of insulin to a patient with diminished first-phase insulin release.
Insulin appears to be more readily absorbed when injected intradermally because of the high degree of vascularity in the intradermal layer. Such quick absorption of injected insulin by the body is beneficial when compensating for diminished first-phase insulin release at mealtime. Accordingly, a need also exists for a drug delivery device that supplies a replacement for first-phase insulin intradermally.
No existing drug delivery device provides only a first-phase insulin dose. Accordingly, a user must set the dose prior to making the injection, which could lead to dose inaccuracies. Accordingly, a need also exists for a drug delivery device that supplies only first-phase insulin without the need to set a dose.
Existing single-use prefilled disposable drug delivery devices, such as that disclosed in U.S. Pat. No. 4,955,871 to Thomas, issued Sep. 11, 1990, are not able to generate the high pressures associated with intradermal injections. A user can generate an injection pressure of approximately 20-30 psi with existing single-use disposable prefilled drug delivery devices. However, intradermal injections require an injection pressure of at least 200 psi. Therefore, a need exists for a pre-filled drug delivery device that generates an injection pressure sufficient for an intradermal injection.